Impact of Design of Experiments in the optimisation of catalytic reactions in academia

Design of Experiments (DoE) is extensively and routinely used in industry; however, in the last decades, it has been gaining increasing interest in organic synthesis in academia. The use of Chemometrics is an attractive strategy to find the real optimum in chemical reactions, especially when affected by several variables. DoE has been applied in a growing number of synthetic transformations over the years, where it can undoubtedly help in the process optimisation, saving costs and time. This review concisely discusses the chemometric basis of Design of Experiments and highlights several examples in which DoE has been applied in organic synthesis. Table of contents 1 Introduction 2 Chemometric basis of DoE 3 DoE applied in catalysis: examples 4 Conclusions

GDP-Mannose 3,5-Epimerase: A View on Structure, Mechanism, and Industrial Potential

GDP-mannose 3,5-epimerase (GM35E, GME) belongs to the short-chain dehydrogenase/reductase (SDR) protein superfamily and catalyses the conversion of GDP-d-mannose towards GDP-l-galactose. Although the overall reaction seems relatively simple (a double epimerization), the enzyme needs to orchestrate a complex set of chemical reactions, with no less than 6 catalysis steps (oxidation, 2x deprotonation, 2x protonation and reduction), to perform the double epimerization of GDP-mannose to GDP-l-galactose. The enzyme is involved in the biosynthesis of vitamin C in plants and lipopolysaccharide synthesis in bacteria. In this review, we provide a clear overview of these interesting epimerases, including the latest findings such as the recently characterized bacterial and thermostable GM35E representative and its mechanism revision but also focus on their industrial potential in rare sugar synthesis and glycorandomization.

Class Map: Improving Students’ Skills of Organic Synthesis in Learning Organic Chemistry for Pre-University Students

This action research uses the Kemmis & Mc Taggart Model (1988) to improve the skills for science stream of pre-university students in organic synthesis topic to convert one functional group to another by using Class Map in learning Organic Chemistry. The objectives of this study were to improve memory skills in conversion of functional groups in an Organic Chemistry reaction and to cultivate students' interest in the subject of Organic Chemistry. A total of six students of 6 Delta 2, SMK Sultan Abu Bakar were involved in this study. Preliminary surveys were conducted through observations, document analysis and interviews. The results of the survey showed that students could not remember the conversion of functional group well because in the Semester Three chemistry syllabus, there are too many chemical reactions, causing students less interested in learning Organic Chemistry. Students were exposed to the Class Map within two months. The test results displayed that (i) students can recall the functional group conversion reaction in an Organic Chemistry and (ii) students can apply the organic reactions learned in answering questions. The findings of the interviews showed that students can cultivate an interest in Organic Chemistry subject.

A method for determining stoichiometric coefficients using minors of a matrix

Spinel materials often have complex structures and as a result, balancing of reactions with these compounds by traditional methods become very time consuming. A method to calculate the stoichiometric coefficients for chemical reactions using first a modified matrix-inverse method and then an optimised method is proposed. Both methods are explored using linear algebra and the result demonstrated using a typical chromite reduction reaction.

A METHOD FOR DETERMINING STOICHIOMETRIC COEFFICIENTS USING MINORS OF A MATRIX

Spinel materials often have complex structures and as a result, balancing of reactions with these compounds by traditional methods become very time consuming. A method to calculate the stoichiometric coefficients for chemical reactions using first a modified matrix-inverse method and then an optimised method is proposed. Both methods are explored using linear algebra and the result demonstrated using a typical chromite reduction reaction.

A Bond Bundle Case Study of Diels-Alder Catalysis Using Oriented Electric Fields

Bond bundles are chemical bonding regions, analogous to Bader atoms, uniquely defined according to the topology of the gradient bundle condensed charge density, itself obtained by a process of infinitesimal partitioning of the three-dimensional charge density into differential zero-flux surface bounded regions. Here we use bond bundle analysis to investigate the response of the charge density to an oriented electric field in general, and the catalytic effect of such a field on Diels-Alder reactions in particular, which in this case is found to catalyze by allowing the transition state valance bond bundle configuration to be achieved earlier along the reaction pathway. Using precise numerical values, we arrive at the conclusion that chemical reactions and electric field catalysis can be understood in terms of intra-atomic charge density redistribution, i.e., that charge shifts within more so than between atoms account for the making and breaking of bonds.

Characterization and Properties of Water-Blown Rigid Polyurethane Foams Reinforced with Silane-Modified Nanosepiolites Functionalized with Graphite

In the present study, a promising flame retardant consisting of 80 wt% silane-modified nanosepiolites functionalized with 20 wt% graphite (SFG) is used to obtain a synergistic effect principally focussed on the thermal stability of water-blown rigid polyurethane (RPU) foams. Density, microcellular structure, thermal stability and thermal conductivity are examined for RPU foams reinforced with different contents of SFG (0, as reference material, 2, 4 and 6 wt%). The sample with 6 wt% SFG presents a slightly thermal stability improvement, although its cellular structure is deteriorated in comparison with the reference material. Furthermore, the influence of SFG particles on chemical reactions during the foaming process is studied by FTIR spectroscopy. The information obtained from the chemical reactions and from isocyanate consumption is used to optimize the formulation of the foam with 6 wt% SFG. Additionally, in order to determine the effects of functionalization on SFG, foams containing only silane-modified nanosepiolites, only graphite, or silane-modified nanosepiolites and graphite added separately are studied here as well. In conclusion, the inclusion of SFG in RPU foams allows the best performance to be achieved.